Recent research conducted by the Veterans Affairs Portland Health Care System has highlighted a significant decline in the effectiveness of a single dose of the respiratory syncytial virus (RSV) vaccine among older adults. This study primarily focuses on veterans aged 60 and above, revealing an initial strong protective effect that diminishes over an 18-month period.

Overview of RSV and Vaccination

Respiratory syncytial virus (RSV) is known to cause severe respiratory illnesses in older adults and individuals with chronic diseases. Due to its implications for health care systems and the associated respiratory mortality in the U.S., RSV vaccinations for this demographic became available in 2023. The vaccines currently circulating include:

  • RSVPreF3 (Arexvy) – Developed by GlaxoSmithKline
  • RSVpreF (Abrysvo) – Developed by Pfizer
  • mRNA-1345 (mRESVIA) – Developed by Moderna

Despite the recommendations for vaccination, coverage remains limited, with only 48% of adults aged 75 years and older and 38% of adults between 60 to 74 years with high-risk conditions having received the vaccine by the end of the 2024–2025 season.

Research Methodology

The study, titled “Durability of Respiratory Syncytial Virus Vaccine Effectiveness Among US Veterans,” was published in JAMA Internal Medicine. It utilized a target trial emulation framework within the Veterans Health Administration (VHA), which has a robust electronic health record system. This allowed researchers to examine vaccination effects across a large cohort of veterans eligible for RSV vaccination.

Demographics of the Study Group

Demographic Percentage
Vaccinated Veterans 301,300 (9.4%)
Unvaccinated Veterans 1,075,893 (90.6%)
Cardiovascular Disease 44.3%
Diabetes 41.0%
Chronic Lung Disease 30.8%
Chronic Kidney Disease 21.0%
Immunocompromised Status 6.5%

Effectiveness Over Time

The findings indicated that while the effectiveness of the vaccine was substantial within the initial weeks post-vaccination (82.5% at 0 to 1 month), there was a significant decline in protective effects over time:

Time Frame Vaccine Effectiveness Outcome Type
0 to 1 Month 82.5% Documented RSV Infections
0 to 18 Months 59.4% Documented RSV Infections
0 to 1 Month 88.9% Hospitalizations
0 to 18 Months 57.3% Hospitalizations

These results indicate that the protection provided by the vaccine not only wanes but also varies significantly across different risk groups. For instance, immunocompromised veterans showed a more pronounced decrease in effectiveness over time compared to their healthier counterparts.

Conclusion and Future Directions

The conclusions from this study reinforce the importance of ongoing evaluations of RSV vaccination strategies, especially for older adults. Given the waning effectiveness observed, particularly in high-risk groups, the study authors suggest that further investigation into the potential benefits of additional doses for these populations may be warranted. This emphasizes a need for continued research in optimizing vaccination strategies to ensure effective protection against RSV.

"This study underscores the critical need for robust vaccination strategies tailored for older individuals and those with compromised immune systems." – Dr. Sadie Harley, Scientific Editor

For further details, please refer to the original article on Medical Xpress.

Literature Cited

[1] Bajema, K. L., et al. (2025). Durability of Respiratory Syncytial Virus Vaccine Effectiveness Among US Veterans, _JAMA Internal Medicine_.

[2] Hung, A., et al. (2025). The Importance of Real-World Evidence to Inform RSV Vaccine Guidance, _JAMA Internal Medicine_.